Opponents said the plan would be unworkably complicated, would pressure states without sales taxes to adopt them and would encourage companies to move overseas, where they said sales taxes could not be enforced.

"It tramples on states' rights," said Sen. Kelly Ayotte, R-N.H.

Online businesses with less than $1 million in annual sales would be exempted from having to collect the levies.

In states with sales taxes, online buyers are currently supposed to pay a tax on their purchases but the requirement is seldom enforced.